Glaucoma Detection and Testing

How is glaucoma diagnosed? Understanding the process is key. Discover all the essential tests your eye doctor uses to accurately assess your risk and protect your vision.

Key Takeaways: Your Glaucoma Detection Action Plan

Glaucoma diagnosis is a thorough, multi-step process that goes far beyond a quick eye pressure check. Here are the most critical insights to protect your vision:

• Diagnosis is Comprehensive, Not Casual: An accurate diagnosis requires 4–5 specialized tests—not just Tonometry (the puff test)—to evaluate eye pressure, optic nerve health, visual field, and cornea thickness.

• Know Your Risk Profile: Be proactive by sharing your full medical history, especially if you have a family history, chronic conditions like diabetes or migraines, or are of African, Hispanic, or Asian descent.

• Normal Pressure Doesn’t Mean Zero Risk: You can still have Normal-Tension Glaucoma even with pressure readings between 12 – 22 mm Hg. Your optic nerve health is always the definitive factor.

• Early Detection Requires Regularity: Since open-angle glaucoma often progresses with zero symptoms, consistent, comprehensive eye exams are the single most important tool for detecting the condition before irreversible vision loss occurs.

• Baseline Data is Critical: Initial glaucoma tests provide a crucial baseline for your eye doctor to compare future measurements against, allowing them to spot subtle changes as you age.

You might be surprised at how many tests eye doctors use to diagnose glaucoma. A proper diagnosis requires careful evaluation of many aspects of your eye’s health – from eye pressure to cornea thickness to the health of your optic nerve. This article describes how your eye doctor assesses your risk and all the tests needed to properly diagnose glaucoma.

Risk Factor Assessment

Your eye doctor will begin by assessing your risk level for developing glaucoma. This will help determine the frequency and extent of testing needed. Through a family history and medical questionnaire, the eye doctor is looking for the following risk factors:

• Over the age of 60
• Ethnic background, such as African or black Caribbean descent, Hispanic, or Asian
• Family history of glaucoma, such as a sibling or parent with glaucoma
• History of eye conditions, injuries, or surgeries
• Prolonged corticosteroid use (eye drops, pills, inhalers, or creams)
• Chronic conditions that affect blood flow, such as migraines, diabetes, and low blood pressure
  pressure or hypertension
• Current or former smoker

If you’ve already had a comprehensive eye exam, your eye doctor will also consider these risk factors:

• Eye pressure higher than normal (above 21 mm Hg)
• Thin corneas (less than 0.5 millimeters)

Your type of eyesight is also important. People with farsightedness are at a higher risk for narrow-angle glaucoma, a more serious type that can advance quickly. While nearsightedness is associated with open-angle glaucoma, which progresses slowly without any symptoms.

Standard Glaucoma Tests

During a comprehensive eye exam, your eye doctor will always check for glaucoma, regardless of the risk level. This provides a baseline for comparison as you age. There are two tests: tonometry and ophthalmoscopy.

Tonometry

Tonometry measures the pressure within your eye. Your eye doctor will give you drops to numb your eyes. Then he/she will use a device called a tonometer, which applies a small amount of pressure with a warm puff of air.

Eye pressure is unique to each person, so it’s not always a reliable indicator for glaucoma. It’s simply another piece of information to help your eye doctor assess your eyes. The range for normal pressure is 12-22 mm Hg (“mm Hg” in millimeters of mercury, a scale for recording eye pressure). Most glaucoma cases are diagnosed with pressure over 20mm Hg. However, some people can have glaucoma at pressures between 12 -22mm Hg.

Ophthalmoscopy

This is an examination of your optic nerve. Your eye doctor will use eye drops to dilate the pupil, which makes it possible to see through your eye to examine the shape and color of the optic nerve. Then, using a small device with a light on the end, your optic nerve is magnified. Based on the results of these tests, your doctor may ask you to have more glaucoma exams.

Supplemental Glaucoma Tests

Perimetry

Perimetry is a visual field test. It creates a map of your complete field of vision. During this test, you’ll look straight ahead and then indicate when a moving light passes your peripheral (or side) vision. Try to relax and respond as accurately as possible. To ensure accuracy, your doctor may repeat the test to see if the results are the same the next time. If you’ve been diagnosed with glaucoma, a visual field test is usually recommended at least once per year to assess changes to your vision.

Gonioscopy

This diagnostic exam helps determine the angle of your iris and cornea. First, you’ll receive eye drops to numb the eye. A hand-held contact lens is gently placed on the eye. A mirror on the contact lens shows the doctor if the angle is closed and blocked (a possible sign of angle-closure or acute glaucoma) or wide and open (a possible sign of open-angle, chronic glaucoma).

Pachymetry

Last, your eye doctor may want to use pachymetry as another way to confirm a diagnosis. Pachymetry measures the thickness of your cornea, the clear window at the front of the eye. A probe called a pachymeter is gently placed on your cornea to measure its thickness. Pachymetry can help clarify your diagnosis because corneal thickness has the potential to influence eye pressure readings.

Further Reading & Citations

For additional, reliable information on glaucoma and eye health, please refer to the following authoritative resources:

• National Eye Institute (NEI): Glaucoma Information and Comprehensive Overview.

• Glaucoma Research Foundation: Information on types, treatments, and ongoing research.

Glaucoma diagnosis is not as simple as you might expect. Be sure to have regular eye exams, especially if you have any of the risk factors, to detect glaucoma early.